Technical Field
The present invention relates to a semiconductor device having an inductor.
Related Art
In some cases, an inductor is provided in conventional matching circuits for MMIC's (monolithic microwave integrated circuit) and the like (for example Japanese Unexamined Patent Publication No. 2002-289782). In addition, in recent years, a voltage control oscillator using the resonation phenomenon of a parallel LC tank circuit is sometimes used as a local oscillator of a PLL (phase locked loop) circuit. An inductor is naturally provided to such a voltage control oscillator (for example, Ali Hajimiri et al., “Design Issues in CMOS Differential LC Oscillators,” IEEE JOURNAL OF SOLID-STATE CIRCUITS, Vol. 34, No. 5, May 1999, pp. 717-724).
FIG. 7 is a plan view schematically showing the MMIC disclosed in Japanese Unexamined Patent Publication No. 2002-289782. An inductor 101, which forms a matching circuit, is formed in this MMIC. In addition, pads 102, to which bumps for flip-chip mounting of the MMIC on a substrate are connected, are formed. The pads 102 are arranged outside the circuit forming region D2 in this MMIC.
The present inventor has recognized as follows. A circuit scale of the MMIC in FIG. 7 is not great, and therefore, the pads 102 can be arranged outside the circuit forming region D2. When the circuit scale becomes great, such as an LSI, however, the number of pads 102 increases, and therefore, the chip size increases, in the case where the pads are arranged outside the circuit forming region D2.
Thus, as shown in FIG. 8, it is considered to arrange pads 102 within the circuit forming region D2. As a result, a great number of pads 102 can be provided without increasing the chip size.
In FIG. 8, however, the magnetic field of an inductor 101 generates an eddy current in pads 102 located above the inductor (hatched portions). Then, this eddy current generates a magnetic field of a polarity so as to cancel the above described magnetic field following Lenz's law, and thus, the strength of the magnetic field lowers. Lowering of the strength of the magnetic field leads to lowering of the Q value.